The invention relates to a method and an apparatus for inserting coils into slots in the cores of electrical machines, the coils being produced on a form and transferred onto an insertion tool consisting of parallel insertion shafts arranged in a circle and an axially driven insertion block, and being drawn thereby into the stator slots.
In the case of certain ratios between the wire size and the width of the space between the insertion shafts as well as other unfavorable factors, the windings tend to jam in the slots when they are advanced by the insertion block along stationary shafts. As a remedy it is known to run together with the insertion block one of two insertion shafts carrying a particular coil strand (cf. DE-PS 19 18 485). It is furthermore known in this connection to run all of the insertion shafts together with the insertion block in the first phase of the insertion process, then to set the free ends of the insertion shafts at approximately the level of the opposite face of the laminated stator core, and lastly to perform the remainder of the insertion movement with the insertion block alone, which in a known manner runs past the free ends of the insertion shafts in order to shape the ends of the coils radially (cf. DE-OS 20 06 526 and DE-AS 26 30 183).
It is a disadvantage that just at the end of the insertion process the insertion block must cover a very long distance while the insertion shafts are already stopped, so that wire jamming can occur. Especially in the case of relatively high coil build-up the entire insertion can be performed but quickly, and then a very long distance must be traveled by the insertion block while the insertion shafts are already at a standstill.
Since the requirements of the winders of compressor motors increase from year to year, and one is striving to improve the efficiency of the motors by not only reducing the size of the stator slots, but also requiring a high fill factor, these new stators can no longer be wound by the insertion method and apparatus known in the state of the art. If it is desired to wind these new stators with, for example, the apparatus of German Patent 26 30 183, it will be found that the insertion stroke with all accompanying shafts through the stator bore and on past the top edge of the stator will work the first time, but the high coil build-up in the slots between the shafts forces the shafts apart at their free upper ends, so that the shafts can not be pulled back down without forcing and this damages the coils.
The invention therefore is addressed to the problem of creating a method and an apparatus of the kind described above by which conditions in the middle and at the end of the insertion process can be improved over the state of the art.
The new method proposed for the solution of the above problem is characterized in that, in a first phase of the insertion process, the insertion block and the short insertion shafts and long insertion shafts are driven synchronously with their upper open ends from a first position through the bore of the stator past the upper edge of the stator to a second position, and that in a second phase the long insertion shafts are retracted to just above the upper edge of the stator, while the insertion block and the short insertion shafts run forward together to a third position, and that in a third phase the insertion block, the short insertion shafts and the long insertion shafts return from the third position to the starting position.
By the proposed method the advantage of all the insertion shafts traveling together is utilized, this movement permitting no relative movement between the coils and the insertion shafts, and thus also there being no danger that the wires may be damaged, while then the stroke of the long insertion shafts is reversed through half the length of the insertion stroke, and on their downward travel halt just above the upper edge of the stator, while the short insertion shafts travel continuously on and upward through the stator and insert the coils completely into the stator. In contrast to the insertion apparatus previously known, because of the retraction of the long insertion shafts not only do the wires move in the slot and do not jam, but the advantage also is that the long insertion shafts open the slot at one end by their retraction, so that the wires are no longer laid one over the other but shrink together in bundles.
To accelerate the last-mentioned advantage it is furthermore proposed that, in the second phase, the long insertion shafts be at least partially retracted before the insertion block and the short shafts travel forward. Now, after a number of wires are therefore no longer stacked one over the other, the long insertion shafts can descend or be withdrawn further, while then the insertion block and the short shafts travel simultaneously forward. In this manner forcible insertion is avoided, and especially the pressure on the insertion shafts is reduced.
In certain cases it is also conceivable to retract long insertion shafts to just above the top edge of the stator and only then move short insertion shafts forward.
As an aid in the insertion process in certain cases it is also proposed that, in the second phase, the long insertion shafts be retracted, while at the same time the insertion block and the short insertion shafts travel forward, or that in the second phase the long insertion shafts with the insertion block and the short insertion shafts run alternately. The last-named parts of the process can be employed if the coil build-up is not too high but a relatively great jamming of the wires in the slot is involved.
To accelerate the insertion process it is furthermore proposed that the insertion block and the short insertion shafts move together out of the starting position at a continuous speed past the second position to the third position. In which case it is then advantageous if the long insertion shafts travel from the second position to the third position at the same speed or a higher speed than the short insertion shafts.
No matter how the individual variants of the method have been described or may yet be set forth, it changes nothing of the basic idea of the invention, that in a middle insertion phase certain insertion shafts are retracted and the others travel forward, and that not only is the slot thereby freed at the top end, but also the wires are favorably influenced by the relative movement of two insertion shafts lying side by side.
The apparatus for the practice of the above-described method is characterized by the fact that, in the first phase of the insertion process, the short insertion shafts fastened to the insertion block are driven by one drive, in synchronism with the long insertion shafts which are fastened to a shaft holder and driven by another drive, from the starting position with its open upper ends past the top edge of the stator to the second position, and that in the second phase the first drive reverses and retracts the shaft holder together with the long insertion shafts to just above the upper edge of the stator, the second drive driving the insertion block forward to the third position, and that in the third phase the drives bring the insertion block and the shaft holder to the starting position.
It is also advantageous that the drives are freely controlled as to their speed and their changes of direction.
It is also advantageous if the insertion block and the short insertion shafts travel together from the starting position at a continuous speed through the second position to the third position, while the long insertion shafts travel from the second to the third position at the same speed or at a higher speed than the short insertion shafts. In the case of a higher speed in the long insertion shafts, a faster downstroke of the shafts takes place and therefore a faster opening of the slot at the top, so that the wires in the slot are no longer stacked one over the other but shrunk together in bundles.
As an aid for the new method it is also proposed to arrange above the top edge of the stator a support means consisting of a holding ring, supporting ring and abutments, which can travel axially if need be. Also radially moving abutments are conceivable but technically more complicated. The supporting means has the advantage that insertion shafts extending free above the top edge of the stator are centered and thus reduce the pressure on the stator teeth and it serves to prevent coil wires from jamming between the insertion shafts.